Seminal, adventitious and lateral root growth and physiological responses in rice to upland conditions.

Understanding the growth and physiological responses of rice to upland conditions would be helpful for designing treatments to improve the tolerance of rice under a rainfed system. The objective of this study was to investigate the initiation,elongation and membrane stability of seminal, lateral and adventitious roots of upland rice after 9-d upland condition treatment. Compared with control roots under waterlogged conditions, upland water deficiency conditions favor seminal and lateral root growth over adventitious root growth by accelerating seminal root elongation, promoting lateral root initiation and elongation, and reducing the elongation and number of adventitious roots. Enhanced total root number and length resulted in increase of total root dry weight and thereby increasing the root-to-shoot ratio. Organic compound leakage from seminal root tips and adventitious roots increased progressively to some extent with upland culture duration, while significant increases in seminal root tips were the consequence of loss of membrane integrity caused by the upland-condition enhanced growth.